RE: [PATCH 2/2] soc: fsl: dpio: use a cpumask to identify which cpus are unused

[Ioana Ciornei]

> >
> > The current implementation of the dpio driver uses a static next_cpu
> > variable to keep track of the index of the next cpu available. This
> > approach does not handle well unbinding and binding dpio devices in a
> > random order. For example, unbinding a dpio and then binding it again
> > with the driver, will generate the below error:
> >
> > $ echo dpio.5 > /sys/bus/fsl-mc/drivers/fsl_mc_dpio/unbind
> > $ echo dpio.5 > /sys/bus/fsl-mc/drivers/fsl_mc_dpio/bind
> > [  103.946380] fsl_mc_dpio dpio.5: probe failed. Number of DPIOs
> > exceeds NR_CPUS.
> > [  103.955157] fsl_mc_dpio dpio.5: fsl_mc_driver_probe failed: -34
> > -bash: echo: write error: No such device
> >
> > Fix this error by keeping a global cpumask of unused cpus that will be
> > updated at every dpaa2_dpio_[probe,remove].
> >
> > Signed-off-by: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> > ---
> >  drivers/soc/fsl/dpio/dpio-driver.c  | 25 ++++++++++++++++---------
> > drivers/soc/fsl/dpio/dpio-service.c |  6 ++++++
> >  include/soc/fsl/dpaa2-io.h          |  2 ++
> >  3 files changed, 24 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/soc/fsl/dpio/dpio-driver.c
> > b/drivers/soc/fsl/dpio/dpio-driver.c
> > index e58fcc9..832175c 100644
> > --- a/drivers/soc/fsl/dpio/dpio-driver.c
> > +++ b/drivers/soc/fsl/dpio/dpio-driver.c
> > @@ -30,6 +30,8 @@ struct dpio_priv {
> >         struct dpaa2_io *io;
> >  };
> >
> > +static cpumask_var_t cpus_unused_mask;
> > +
> >  static irqreturn_t dpio_irq_handler(int irq_num, void *arg)  {
> >         struct device *dev = (struct device *)arg; @@ -86,7 +88,7 @@
> > static int dpaa2_dpio_probe(struct fsl_mc_device *dpio_dev)
> >         struct dpio_priv *priv;
> >         int err = -ENOMEM;
> >         struct device *dev = &dpio_dev->dev;
> > -       static int next_cpu = -1;
> > +       int possible_next_cpu;
> >
> >         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >         if (!priv)
> > @@ -128,17 +130,14 @@ static int dpaa2_dpio_probe(struct fsl_mc_device
> *dpio_dev)
> >         desc.dpio_id = dpio_dev->obj_desc.id;
> >
> >         /* get the cpu to use for the affinity hint */
> > -       if (next_cpu == -1)
> > -               next_cpu = cpumask_first(cpu_online_mask);
> > -       else
> > -               next_cpu = cpumask_next(next_cpu, cpu_online_mask);
> > -
> > -       if (!cpu_possible(next_cpu)) {
> > +       possible_next_cpu = cpumask_first(cpus_unused_mask);
> > +       if (possible_next_cpu >= nr_cpu_ids) {
> >                 dev_err(dev, "probe failed. Number of DPIOs exceeds NR_CPUS.\n");
> >                 err = -ERANGE;
> >                 goto err_allocate_irqs;
> >         }
> > -       desc.cpu = next_cpu;
> > +       desc.cpu = possible_next_cpu;
> > +       cpumask_clear_cpu(possible_next_cpu, cpus_unused_mask);
> >
> >         /*
> >          * Set the CENA regs to be the cache inhibited area of the
> > portal to @@ -211,7 +210,7 @@ static int dpaa2_dpio_remove(struct
> > fsl_mc_device *dpio_dev)  {
> >         struct device *dev;
> >         struct dpio_priv *priv;
> > -       int err;
> > +       int err = 0, cpu;
> >
> >         dev = &dpio_dev->dev;
> >         priv = dev_get_drvdata(dev);
> > @@ -220,6 +219,9 @@ static int dpaa2_dpio_remove(struct fsl_mc_device
> > *dpio_dev)
> >
> >         dpio_teardown_irqs(dpio_dev);
> >
> > +       cpu = dpaa2_io_get_cpu(priv->io);
> > +       cpumask_set_cpu(cpu, cpus_unused_mask);
> > +
> >         err = fsl_mc_portal_allocate(dpio_dev, 0, &dpio_dev->mc_io);
> >         if (err) {
> >                 dev_err(dev, "MC portal allocation failed\n"); @@
> > -267,11 +269,16 @@ static int dpaa2_dpio_remove(struct fsl_mc_device
> > *dpio_dev)
> >
> >  static int dpio_driver_init(void)
> >  {
> > +       if (!zalloc_cpumask_var(&cpus_unused_mask, GFP_KERNEL))
> > +               return -ENOMEM;
> > +       cpumask_copy(cpus_unused_mask, cpu_online_mask);
> > +
> >         return fsl_mc_driver_register(&dpaa2_dpio_driver);
> >  }
> >
> >  static void dpio_driver_exit(void)
> >  {
> > +       free_cpumask_var(cpus_unused_mask);
> >         fsl_mc_driver_unregister(&dpaa2_dpio_driver);
> >  }
> >  module_init(dpio_driver_init);
> > diff --git a/drivers/soc/fsl/dpio/dpio-service.c
> > b/drivers/soc/fsl/dpio/dpio-service.c
> > index 21c3e32..3198265 100644
> > --- a/drivers/soc/fsl/dpio/dpio-service.c
> > +++ b/drivers/soc/fsl/dpio/dpio-service.c
> > @@ -214,6 +214,12 @@ irqreturn_t dpaa2_io_irq(struct dpaa2_io *obj)
> >         return IRQ_HANDLED;
> >  }
> >
> > +int dpaa2_io_get_cpu(struct dpaa2_io *d) {
> > +       return d->dpio_desc.cpu;
> > +}
> > +EXPORT_SYMBOL(dpaa2_io_get_cpu);
> 
> Although this function is very simple function and probably self-explanatory, it is
> required that exported APIs have a kernel-doc comment just like other functions
> in the file.

Sorry for that. Will send an updated version to fix this.

Ioana

> 
> > +
> >  /**
> >   * dpaa2_io_service_register() - Prepare for servicing of FQDAN or CDAN
> >   *                               notifications on the given DPIO service.
> > diff --git a/include/soc/fsl/dpaa2-io.h b/include/soc/fsl/dpaa2-io.h
> > index ab51e40..1c1764f 100644
> > --- a/include/soc/fsl/dpaa2-io.h
> > +++ b/include/soc/fsl/dpaa2-io.h
> > @@ -90,6 +90,8 @@ struct dpaa2_io_notification_ctx {
> >         void *dpio_private;
> >  };
> >
> > +int dpaa2_io_get_cpu(struct dpaa2_io *d);
> > +
> >  int dpaa2_io_service_register(struct dpaa2_io *service,
> >                               struct dpaa2_io_notification_ctx *ctx);
> > void dpaa2_io_service_deregister(struct dpaa2_io *service,
> > --
> > 1.9.1
> >